Disaggregated star platform management bus architecture system

ABSTRACT

A star topology platform management bus architecture and system that provides disaggregation of the platform control element portion and the routing element portion of a central management controller, which provides for physical design efficiency as well as other advantages.

BACKGROUND

1. Field of the Invention

The present invention relates generally to the field of platform management systems, and more specifically to a disaggregated star platform management bus architecture.

2. Description of Related Art

Computers and other electronic systems often include features with the ability to monitor and control the health and operation of the system hardware. These features may be referred to as platform management, system management, hardware management, etc. Platform management features may include the monitoring and control of temperatures, voltages, fans, power supplies, and other features. Platform management may also include the identification of failed hardware components.

One widely used framework for platform management is the Intelligent Platform Management Interface (IPMI), which specifies key agents involved as well as command sets and data formats for sensors, event logs and sensor data record access, as well as inventory information regarding the Field Replaceable Units (FRUs) that comprise a system.

A platform management system is typically composed of hardware, firmware, and software embedded within an electronic system for the purpose of monitoring and control of the system's operation. This management is typically performed independently of the main processor(s) and operating system of the system. One of the components that may be used to control platform management functions is a central management controller. A central management controller may be based on a microprocessor, application specific integrated circuit, or other type of processing unit and is the principal platform management entity in a system. (In IPMI, the central management controller is referred to as the baseboard management controller.) The central management controller may work with satellite management controllers in the system, some of them integrated on independent FRUs. When an FRU incorporates a satellite management controller, it is referred to as an intelligent FRU. The central management controller can monitor a myriad of operational aspects affecting or detailing the health of the system through any one or more of the satellite management controllers. Typically, each of the intelligent FRUs, including front boards, in a chassis or shelf has a satellite management controller, each of which is in communication with sensors and other components used to monitor and control devices on that FRU or on other FRUs it represents. Another typical responsibility of a central management controller is to represent the chassis or shelf and its constituent FRUs to higher level management entities, often via a network (perhaps Ethernet) link. “Shelf” is often used in the telecommunications industry instead of the more familiar term “chassis”.

Typical prior art platform management control applications utilize a single physical bus—Intelligent Platform Management Bus (IPMB) in IPMI contexts—to link the central management controller with any satellite management controllers in the system. In such single bus systems, all of the communications sent to any of the satellite management controllers are sent to all controllers that are communicatively linked to the physical bus. An advantage of a single physical bus is economy; with only one physical bus, one does not need to route isolated communication lines to each of satellite management controllers but can instead utilize common communication lines with shared access by all management controllers.

In United States Patent Application Publications US 2003/0152074 A1, to Hawkins et al., entitled “Switched Platform Management Architecture and Related Methods”, and US 2003/0130969 A1, to Hawkins et al., entitled “Star Intelligent Platform Management Bus Topology”, a star topology with multiple logical buses is introduced. This approach utilizes physically disparate interconnect segments to each set of one or more satellite management controllers such that each set is communicatively isolated from the other sets. Although this approach provides some fault tolerance and other benefits, the star topology has a distinct disadvantage of requiring the routing of many wires, which comprise the multiple logical buses, from the board upon which the central management controller is located. This disadvantage can be especially important in the context of standardized modular platforms, where most of the pins available on a board may be allocated to specific purposes and insufficient in number to handle that many signals.

SUMMARY

A star topology platform management bus architecture and system that provides disaggregation of the platform control element portion and the routing element portion of a central management controller provides for physical design efficiency as well as other advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a conventional intelligent platform management bus (IPMB) architecture.

FIG. 2 is a block diagram illustrating a star intelligent platform management bus (IPMB) architecture.

FIG. 3 is a block diagram illustrating a disaggregated star platform management bus system according to an embodiment of the present invention.

FIG. 4 is a block diagram illustrating the platform control element and routing element of a disaggregated star platform management bus system according to an embodiment of the present invention.

FIG. 5 illustrates a disaggregated star platform management bus system utilizing a single platform control element and a single routing element according to an embodiment of the present invention.

FIG. 6 illustrates a disaggregated star platform management bus system utilizing dual platform control elements and two routing elements according to an embodiment of the present invention.

FIG. 7 illustrates a disaggregated star platform management bus system utilizing a single platform control element and two routing elements according to an embodiment of the present invention.

FIG. 8 illustrates a partial side view of a board mounted in a shelf according to one embodiment of the present invention.

FIG. 9 illustrates a front view of a shelf according to some embodiments of the present invention.

FIG. 10 illustrates a disaggregated star platform management bus system utilizing two platform control elements and two routing elements according to an embodiment of the present invention.

FIG. 11 illustrates a disaggregated star platform management bus system utilizing two platform control elements and four routing elements according to an embodiment of the present invention.

FIG. 12 illustrates a disaggregated star platform management bus system according to an embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 illustrates an example of a conventional IPMB architecture 120. IPMB (current version 1.0, revision 1.0, Nov. 15, 1999, published by Intel Corporation, Hewlett-Packard Corporation, NEC Corporation, and Dell Computer Corporation) is the main means for in-system platform management information exchange among management controllers in the IPMI architecture. The current versions of the IPMI specification are 1) version 1.5, revision 1.1, Feb. 20, 2002 and 2) version 2.0, revision 1.0, Feb. 12, 2004; both are published by Intel Corporation, Hewlett-Packard Corporation, NEC Corporation, and Dell Computer Corporation. In this example, a central management controller (central MC) 121 is communicatively linked to a plurality of satellite management controllers (satellite MCs) 123, 124, 125 via a single intelligent platform management bus (IPMB) 122. Although three satellite control elements are illustrated here, it is understood that any number of such satellite management controllers may be present utilizing this architecture. The IPMB 122 is typically an addressable serial bus. In the conventional IPMI architecture, a single physical bus is used. With such a single physical bus approach, a single logical bus is used, as well. The IPMB 122 is used to communicate with all of the satellite MCs 123, 124, 125 and thus each of the satellite MCs receives all of the communications directed to any of the satellite MCs.

A platform management system may perform tasks such as sending and receiving platform management information, controlling platform management functions, and recording platform management information. For example, a platform management system may receive and log an indication from a temperature sensor that it is sensing a temperature above a configured threshold, and in response, may send a command to increase fan speed.

One of the controllers in a system may perform the role of the central management controller for the system, in which case it may perform central system management functions such as logging events, collecting field replaceable unit (FRU) inventory information, etc. In addition to these system-internal responsibilities, a central management controller may be responsible to represent the system to higher level management entities, typically via a network link. In conventional IPMI terminology, the central management controller for a system is usually referred to as the baseboard management controller (BMC) for the system. In the modular platform architectures according to some embodiments of the present invention, “central” is a more appropriate adjective because there may be no single “baseboard” as might be present in a conventional server. In some embodiments, redundancies are built into the system resulting in more than one CMC in a system. It is common for a system to have only one active central management controller. Non-central management controllers may be referenced as satellite management controllers (SMCs). An SMC may perform platform management for a particular part or feature of a system. For example, a system may contain a number of circuit boards and other components that are connected by buses, with one board containing a central management controller for that system and other boards containing SMCs. SMCs are typically resident on FRUs, which include front boards and other types of components.

In the IPMI-based IPMB configuration 120 the central MC 121 typically monitors a variety of management functions for the electronic platform in which it resides. The satellite MCs 123, 124, 125 may reside on different boards within an electronic chassis. Each satellite MC may itself provide communication links to various control and monitoring devices for the board on which it resides.

FIG. 2 illustrates an example of a star intelligent platform management bus (IPMB) architecture 220. Instead of a single physical IPMB communicatively linking the central MC to all of the satellite MCs, each of the satellite MCs 222, 223, 224, 225, has an independent physical bus segment 226, 227, 228, 229 which communicatively links it to the central MC 221. The independent physical nature of these bus segments allows for fault isolation. The independent physical bus architecture allows any one of the independent physical bus segments 226, 227, 228, 229 to be operated as an independent logical bus. Embodiments utilizing an independent logical bus architecture allow various features in addition to fault isolation. For instance, message content on one logical bus can be isolated from message content on another logical bus, thus enhancing security. This may be important if intelligent FRUs on different logical buses have different owners. Nevertheless, the combination of the logical buses can be operated conceptually as a single architectural bus that plays the same architectural role for platform management as the single physical IPMB 122 of FIG. 1.

In some embodiments of the present invention, as seen in FIG. 3, a platform management system 320 includes a platform control element 321. The platform control element 321 is communicatively linked with a routing element 323 via a root segment 322. The demarcation line 328 illustrates the disaggregation of the platform control element 321 and the routing element 323. The platform control element 321 resides upon a field replaceable unit (FRU) in some embodiments. In some embodiments, the FRU upon which the platform control element resides is a front board. The routing element 323 resides off of the FRU upon which the platform control element 321 resides. The routing element 323 is communicatively linked to satellite MCs 325, 327 via branch segments 324, 326. There may be any number of satellite MCs in some embodiments. The demarcation line 329 illustrates how the satellite MCs reside on other FRUs, such as front boards, in some embodiments.

In some embodiments, the platform management system 320 resides within an electronic platform compliant to one or more open architectures for modular platforms, such as those developed by the PCI Industrial Computer Manufacturers Group (PICMG).

One such open modular architecture is PICMG 3.0, the Advanced Telecommunications Computing Architecture (AdvancedTCA or ACTA) specification, revision 1.0, as approved on Dec. 30, 2002, and amended by Engineering Change Notice 3.0-1.0-001 (21 Jan. 2004). The basic elements of a PICMG 3.0 platform are front boards, rear transition modules (RTMs), the backplane, and the subrack, along with other shelf-specific FRUs. On the front board, three connector zones are defined: zone 1 for power and shelf management connections; zone 2 for Data Transport Interface; and zone 3 for user-defined Input/Output (I/O) interconnect. Front boards plug into slots on the backplane that contain corresponding connectors in one or more of these zones. The subrack provides standardized mechanical support elements for the slots, such as guide rails and alignment pins.

Another such architecture is PICMG 2.5x, the Compact Telecommunications Computing Architecture (CompactTCA or cTCA) specification, currently in development and available in draft form as revision 0.80. PICMG 2.5x platforms have the same basic elements as PICMG 3.0 platforms (including front boards, rear transition modules, the backplane and the subrack, plus other shelf-specific FRUs), but there are many differences in detail. The CompactTCA connectors most relevant to this application are P1 and P2 on boards (referenced as J1 and J2 at the corresponding backplane positions). Management-oriented pins are primarily in P1, with potential for P2 usage as well. One key difference between the CompactTCA and ATCA PICMG telecommunications computing architectures is in the topology for the main IPMB, which is referenced in both architectures as IPMB-0. AdvancedTCA uses a duplex IPMB-0 comprising two architectural buses IPMB-A and IPMB-B, while CompactTCA uses a simplex IPMB-0 comprising a single architectural bus IPMB-A.

In both the AdvancedTCA and CompactTCA frameworks, the central management controller function of the present invention, which includes both a platform control element and a routing element, is referred to as the “shelf manager”.

For purposes of this application, CompactTCA is very similar to a combination of two predecessor specifications: PICMG 2.16, the CompactPCI Packet Switched Backplane specification and PICMG 2.9, the CompactPCI System Management specification. References to CompactTCA can be assumed to refer to the predecessor specifications also, unless otherwise indicated.

Additionally, PICMG AMC.0, the Advanced Mezzanine Card (AdvancedMC) specification, defines a hot-swappable mezzanine FRU format for AdvancedTCA carrier boards. The main relevance of the AdvancedMC specification to the present invention is the use of an AdvancedMC mezzanine as a standardized FRU on which to implement the platform control element as an additional way to take advantage of the flexibility offered by disaggregation of star platform management bus architectures.

In some embodiments, the platform control element 321 resides upon an FRU. In some embodiments, the FRU upon which the platform control element 321 resides is in an FRU position dedicated to that purpose and located outside the subrack that contains the standardized front board positions and which is therefore essentially free of specification constraints regarding form factor and connector attachments to the backplane. In some embodiments, the FRU upon which the platform control element 321 resides is a front board, thereby inheriting the constraints on front boards imposed by the relevant specification. Alternatively, in some embodiments, the platform control element could reside on an AdvancedMC FRU installed on an AdvancedTCA front board. In this latter case the platform control element is subject to the constraints of both: 1) ATCA front boards that are AdvancedMC carriers and 2) AdvancedMCs, themselves. The routing element 323 resides off of the FRU upon which the platform control element 321 resides. In some embodiments, the routing element 323 is on a separate FRU. In some embodiments, the routing element 323 resides in an air plenum or other shelf-specific location. In some embodiments, the root segment 322 which communicatively links the platform control element 321 and the routing element 323 may consist of a pair of wires. In some embodiments, the root segment 322 which communicatively links the platform control element 321 and the routing element 323 may consist of four wires or possibly two pairs of wires. For example, the root segment may use a separate pair of wires for each direction of communication. The root segment 322 may be routed through two or more of the eight pins allocated under ACTA for connectivity on the zone 2 connector between Ethernet hubs (base interface hubs, in ATCA terms) and dedicated central management controller FRUs (dedicated shelf management controllers, in ATCA terms).

In some embodiments, the branch segments 324, 326, although physically separate, may be part of a single logical bus. In such an embodiment, communications for any of the satellite MCs are sent to all of the satellite MCs along each of the branch segments. In some embodiments, there is a plurality of logical buses among the branch segments. A first branch segment 326 may have its own logical bus; communication sent along the branch segment in such an embodiment may be limited to communication to and from the first satellite MC 327. Similarly, the second branch segment 324 may have its own logical bus, and communications sent along this logical bus in such an embodiment may be limited to communication to and from the second satellite MC 325. In embodiments with a plurality of logical buses, the routing element 323 may selectively route communications for particular satellite management controller only via the logical bus that includes the branch segment which links the routing element 323 and that particular satellite management controller.

In an embodiment using a plurality of logical buses with the platform control element residing on a front board, but with the routing element residing off of the front board, the number of wires required to be routed from the front board is significantly reduced. This may be particularly advantageous as wires routed from a front board typically route through a limited number of connectors whose pin assignments are largely or entirely pre-defined by industry standards. With the routing element located off of the front board, the root segments between the platform control element and the routing element may be routed through the connectors, but the (typically) far more numerous branch segments originate from a location off of the front board and therefore are not routed en masse through these limited connector spaces. This allows the benefits of star topology to be achieved even when the platform control element resides on a front board, or optionally on a front board. Thus, the central management controller can be located very flexibly in the shelf.

FIG. 4 illustrates a configuration 350 of the platform management system according to some embodiments of the present invention. The platform control element 321 may consist of a control logic portion 351, a memory portion 352, and a management application portion 353. The platform control element 321 is communicatively linked to the routing element 323 by the root segment 322.

The demarcation line 328 indicates the disaggregation of the platform control element 321 and the routing element 323. The routing element 323 may consist of a router 354, and an I/O interface 355. The branch segments 357, 358, 359 communicatively link the routing element 323 to satellite MCs elsewhere in the system.

In some embodiments of the present invention, as seen in FIG. 5, a platform management system 500 comprises a platform control element 502 residing upon an FRU 501. In this illustrative embodiment, the platform control element 502 resides upon a front board. A routing element 504 is communicatively linked to the platform control element 502 via a root segment 503. The routing element 504 is communicatively linked to a plurality of satellite management controllers 513, 514, 515, 516 via a plurality of branch segments 509 a-d. The routing element 504 resides upon an FRU 510. The satellite management controllers 513, 514, 515, 516 reside upon on a plurality of FRUs 505, 506, 507, 508 in some embodiments. In this illustrative embodiment, some of the FRUs 506, 507, 508 are front boards. The number and type of FRUs may vary across platform management applications, and the number of satellite management controllers may vary across platform management applications. In some embodiments, the front board 501 wherein the platform control element 502 resides may also have a satellite control element communicatively linked to the routing element 504. In some embodiments, routing element 504 may include communication links to devices other than intelligent FRUs, with platform control element 502 adapted to manage those links via root segment 503 and routing element 504. In some such embodiments, the additional devices could implement fan control and monitoring or temperature monitoring.

In some embodiments, the branch segments 509 a-d may be part of a single logical bus. In such an embodiment, communications for all of the satellite MCs are sent to all of the satellite MCs along each of the branch segments. In some embodiments, there is a plurality of logical buses among the branch segments. A first branch segment 509 a may be its own separate logical bus; communication sent along the branch segment in such an embodiment may be limited to communication to and from the first satellite MC 513 which resides upon a first front board 505. Similarly, a second branch segment 510 b may be its own separate logical bus, and communications sent along this logical bus in such an embodiment may be limited to communication to and from the second satellite MC 514 which resides upon a second front board 506. In some embodiments, each of the branch segments is part of a unique logical bus. In some embodiments, there is a plurality of logical buses, but a single logical bus may utilize more than one of the branch segments. In embodiments using a plurality of logical branch buses, the routing element may selectively route communications between the platform control element and the SMCs that are communicatively linked to a particular logical branch bus. The routing element may also selectively route communications from the SMCs that are communicatively linked to a first logical branch bus to the SMCs that are communicatively linked to a second logical branch bus.

In embodiments using a plurality of branch segments, the opportunities for fault isolation are enhanced. If the satellite MC on one of the physical branch segments is disrupting system operation, that segment can be isolated so that the rest of the shelf can return to normal operation. The disrupting satellite MC and the FRU upon which it resides can be replaced later. This ability to effectively repair a system disrupted by such a fault via isolating the disruptive branch segment and satellite MC, yields a drastic reduction in Mean Time To Repair (MTTR). The fault isolation advantages are available regardless of whether the physical branch segments are separated into distinct logical buses.

In embodiments using a plurality of logical branch buses, the system yields additional advantages. For example, the plurality of logical branch buses allows for address isolation between logical buses. All participants in a logical or physical IPMB must have distinct IPMB addresses. In contrast, address assignments can be completely independent between distinct logical buses.

Another advantage of a plurality of logical branch buses is that bandwidth can be dedicated for each logical branch bus. A satellite MC on a distinct logical branch bus can use the entire bandwidth of the branch bus to communicate with the associated routing element. Dedicated bandwidth for each satellite MC is also a benefit in scenarios with a high volume of IPMI messages. Such high volumes can occur when a shelf is started or a board is hot-inserted or during periods when problems, such as high temperatures, affect several intelligent FRUs at once and possibly many sensors of each. Sharing a single 100 kHz IPMB for all this messaging can significantly slow the shelf manager's ability to receive, process, and respond to events in the shelf in such circumstances.

Other advantages of a plurality of logical branch buses include the use of different protocols on each logical branch bus and message content isolation between logical branch buses.

In some embodiments, the platform management system 500 is consistent with PICMG 2.5x or CompactTCA. Embodiments consistent with cTCA require radial board control signals managed by the central management controller. In such embodiments, the FRU on which the routing element resides may also include the fan out of the pairs of radial board control signals that CompactTCA requires, one pair for each front board slot. The current draft CompactTCA specification omits the concept of a central management controller (shelf manager) on a front board, because insufficient pins are available on a front board to route potentially tens of such required radial board control signals from the front board to the backplane. Using disaggregation, however, such a configuration is feasible, with the required radial board control signals for each front board slot all emanating from the FRU on which the routing element resides, or another FRU communicatively linked to the platform control element.

In some embodiments, the branch segments 509 b-d are routed to their respective satellite management controllers 514, 515, 516 via two pins in the PI connector of the front boards 506, 507, 508 and similarly to a satellite management controller on a non-front board FRU 513 via two FRU-specific pins. As seen in FIG. 5, the disaggregation of the platform management system 500 significantly reduces the number of lead outs from the front board 501 via the Px connectors.

A CompactTCA system implements a simplex IPMB-0. In the platform management system 500 of FIG. 5, the root segment 503, the routing element 504 and the branch segments 509 a-d constitute the simplex IPMB-0.

In some embodiments, as seen in FIG. 6, a platform management system 700 utilizes two platform control elements and two routing elements. A first platform control element 703 resides upon a first FRU 701. In this illustrative embodiment, the platform control element 703 resides upon a front board. A second platform control element 704 resides upon second FRU 702. In this illustrative embodiment, the platform control element 704 resides upon a front board. In some embodiments, the first platform control element and the second platform control element are adapted to provide central management controller functions on a redundant basis. In some embodiments, the platform control elements may reside upon the same FRU.

A first routing element 706 is communicatively linked to the first platform control element 703 via a first root segment 707. The second routing element 718 is communicatively linked to the second platform control element 704 via a second root segment 708. The first routing element 706 resides upon a third FRU 705. The second routing element 718 resides upon a fourth FRU 719. In some embodiments, the routing elements may reside upon the same FRU. Although the platform management system 700 has two platform control elements 703, 704, as well as two routing elements 706, 718, this embodiment is a simplex IPMB-0 system. Each SMC (SMC 715, for example) has a single IPMB-0 port. Thus, the two branch segments (709 b, 720 b, for example) that link to a single SMC (715, in this example) would be co-terminated at the same single port. This embodiment is a redundant central MC system with redundant platform control elements 703, 704, as well as redundant routing elements 706, 718. Therefore, the IPMB-0 port of each SMC (SMC 715, for example) is communicatively linked to both routing elements 706 and 718 and thereby to both platform control elements 703 and 704. This redundant central MC, simplex IPMB-0 embodiment may be used in a CompactTCA compliant system.

The first routing element 706 is communicatively linked to a plurality of satellite management controllers 713, 714, 715, 716, 717 via a first plurality of branch segments 709 a-e. The second routing element 718 is communicatively linked to a plurality of satellite management controllers 713, 714, 715, 716, 717 via a second plurality of branch segments 720 a-e. The satellite management controllers reside upon on a plurality of FRUs. In this illustrative embodiment, some of the FRUs 701, 702, 710, 711 are front boards. One FRU 712 is not a front board in this embodiment. The number and type of FRUs may vary across platform management applications, and the number of satellite management controllers may vary across platform management applications.

A satellite MC 713 resides upon the first FRU 701 upon which the first platform control element 703 resides. A satellite MC 714 resides upon the second FRU 702 upon which the second platform control element 704 resides. The FRUs upon which the platform control elements reside may or may not have a satellite MC, depending upon the application.

In some embodiments of the present invention, as seen in FIG. 7, a platform management system 530 consists of a platform control element 551 residing upon an FRU 550. In this illustrative embodiment, the platform control element 551 resides upon a front board. Two routing elements 554, 555 are communicatively linked to the platform control element 551 via duplex root segments 552, 553. The platform control element 551 is communicatively linked to a first routing element 554 via a first root segment 552. The platform control element 551 is communicatively linked to a second routing element 555 via a second root segment 553.

The first routing element 554 is communicatively linked to a plurality of satellite management controllers 560, 561, 562, 563 via a plurality of branch segments 559 a-d. The first routing element 554 is disaggregated from the platform control element 551. The first routing element 554 resides upon an FRU 556. The second routing element 555 is communicatively linked to a plurality of satellite management controllers 560, 561, 562, 563 via a plurality of branch segments 558 a-d. The second routing element 555 is disaggregated from the platform control element 551. The second routing element 555 resides upon an FRU 557. In some embodiments, the routing elements may reside upon the same FRU.

In this embodiment, there are two architectural buses, which may be referred to as the A bus and the B bus. Typically, one of the routing elements linked to the platform control element will be part of the A architectural bus, while the other routing element will be part of the B architectural bus.

In an ATCA environment, there are two architectural buses. In such a duplex IPMB-0 system, one of the architectural buses, with its root segment, and its associated routing element and branch segments, is referred to as IPMB-A, and the other architectural bus, with its root segment, and its associated routing element and branch segments, is referred to as IPMB-B. A satellite MC in an ATCA environment has an A port and a B port. Using platform management system 530 as an illustrative embodiment of an ATCA compliant system, for example, the IPMB-A root segment 552 linked to routing element 554 would communicate to the satellite MCs 560, 561, 562, 563 using branch segments 558 a-d which are communicatively linked to the A ports of the satellite MCs.

In some embodiments, there is a plurality of logical buses among the branch segments. Each physical branch segment may have its own logical bus; communication sent along the logical branch bus in such an embodiment may be limited to communication to and from a single satellite MC. In some embodiments, there is a plurality of logical buses, but a single logical bus may utilize more than one of the branch segments.

In embodiments using a plurality of logical branch buses, the routing element may selectively route communications between the platform control element and the SMCs that are communicatively linked to a particular logical branch bus. The routing element may also selectively route communications from the SMCs that are communicatively linked to a first logical branch bus to the SMCs that are communicatively linked to a second logical branch bus.

The satellite management controllers reside upon on a plurality of FRUs 564, 565, 566, 567. In this illustrative embodiment, some of the FRUs 565, 566, 567 are front boards. The number and type of FRUs may vary across platform management applications, and the number of satellite management controllers may vary across platform management applications. In some embodiments, the front board 550 wherein the platform control element 551 resides may also have a satellite management controller communicatively linked to the first routing element 554.

In some embodiments, as seen in FIG. 8, the platform management system 580 is utilized in an electronic platform consistent with the PICMG ACTA or cTCA specifications. Some details of the pictured embodiment in FIG. 8 are specific to ATCA, but the description below covers embodiments consistent with either ATCA or cTCA. The platform control element 502 resides upon a front board 521. The root segment consists of two or more sub-segments, a first sub-segment 522 which routes the root segment from the platform control element 502 to the zone 2 (ATCA) or P2 (cTCA) connector 524, and a second sub-segment 523 which routes the root segment from the zone 2/P2 connector 524 to the switching element 504. In some embodiments, connector 524 may be a zone 1/P1 connector. The front board 521 is mounted to the rear transition module (RTM) 525. In some embodiments, the routing element 504 is mounted in an air plenum 530, typically outside the subrack. A demarcation line 532 on FIG. 8 approximates the boundary between the subrack, where the front board 521 is mounted, and the air plenum above it.

A satellite MC 529 is mounted on the front board 521. The satellite MC 529 is communicatively linked to the routing element 504 via a branch segment. The branch segment is comprised of at least two sub-segments. A first branch sub-segment 590 routes the branch bus from the satellite MC to the zone 1 (ATCA) or P1 (cTCA) connector 526. A second branch sub-segment 531 routes the branch segment from the zone 1/P1 connector 526 to the routing element 504. The zone 3 (ATCA) and other connector(s) (cTCA) 527 are not utilized for platform management purposes in this embodiment.

FIG. 9 illustrates a partial front view of a shelf showing potential mounting locations for FRUs used in platform management according to some embodiments of the present invention. A plurality of front boards (906, 907, 908, for example) are mounted in a shelf in the standardized subrack area. An air plenum 910 above the subrack 909 allows for the possible placement of FRUs 900, 901. The FRUs may contain routing elements or platform control elements in some embodiments. An air plenum 911 below the subrack 909 allows for the possible placement of FRUs 902, 903. The FRUs may contain routing elements or platform control elements in some embodiments. FRUs 904, 905 may also be mounted along the end of the subrack and may contain routing elements or platform control elements in some embodiments. Space and cooling capacity for such FRUs outside the subrack is often highly constrained. The disaggregation of routing elements and platform control elements according to some embodiments of the present invention can simplify meeting those constraints.

In some embodiments of the present invention, a FRU may itself have replaceable modules. In embodiments based on the AMC.0 specification, the replaceable modules are referred to as AdvancedMCs, and plug into a carrier that is an AdvancedTCA board. In some such embodiments, the platform control element resides on an AdvancedMC, where both the AdvancedMC and its carrier board are adapted to support that usage. In such embodiments of the present invention, a star topology platform management bus architecture and AdvancedMC-based platform control elements can be practical, where otherwise this combination would likely not be practical. Other embodiments of the present invention involving FRUs mounted on other FRUs are possible.

In some embodiments, as seen in FIG. 10, a platform management system 600 utilizes two platform control elements 603, 604. In this illustrative embodiment the two routing elements 605, 606 are not located on either of the FRUs upon which the platform control elements 603, 604 are located. In some embodiments, the two platform control elements 603, 604 reside on two separate front boards 601, 602. In some embodiments, the platform control elements may reside upon FRUs of another type. In some embodiments, the platform control elements may reside upon the same FRU. A first platform control element 604 is communicatively linked to each of two routing elements 605, 606 via duplex root segments 622, 623. A second platform control element 603 is communicatively linked to each of two routing elements 605, 606 via duplex root segments 620, 621. In some embodiments, the routing elements reside upon separate FRUs. In some embodiments, the routing elements reside upon the same FRU. In some embodiments, the two platform control elements 603, 604 are adapted to provide central management controller functions on a redundant basis. In some such embodiments, one of the platform control elements is in an active mode while the other platform control element is in a standby mode.

In this embodiment, there are two architectural buses, which may be referred to as the A architectural bus and the B architectural bus. Typically, one of the routing elements linked to each of the platform control elements will be part of the A architectural bus, while the other routing element will be part of the B architectural bus.

In an ATCA environment, there are two architectural buses. One of the architectural buses, with its root segment, and its associated routing element and branch segments, is referred to as IPMB-A, and the other architectural bus, with its root segment, and its associated routing element and branch segments, is referred to as IPMB-B. A satellite MC in an ATCA environment has an A port and a B port. Using platform management system 600 as an illustrative embodiment, for example, the IPMB-A root segment 622 linking the first platform control element 604 to the first routing element 606 would communicate to the satellite MCs 607, 608, 609, 610, 611 using branch segments 625 a-e, which are communicatively linked to the A ports of the satellite MCs. The IPMB-A root segment 620 linking the second platform control element 603 to the first routing element 606 would communicate to the satellite MCs 607, 608, 609, 610, 611 using branch segments 625 a-e, which are communicatively linked to the A ports of the satellite MCs.

The IPMB-B root segment 623 linking the first platform control element 604 to the second routing element 605 would communicate to the satellite MCs 607, 608, 609, 610, 611 using branch segments 626 a-e, which are communicatively linked to the B ports of the satellite MCs. The IPMB-B root segment 621 linking the second platform control element 603 to the second routing element 605 would communicate to the satellite MCs 607, 608, 609, 610, 611 using branch segments 626 a-e, which are communicatively linked to the B ports of the satellite MCs. In this embodiment, each of the platform control elements uses the same routing element for IPMB-A and IPMB-B, respectively; each routing element is shared by both platform control elements for either IPMB-A or IPMB-B.

A plurality of satellite management controllers 607, 608, 609, 610, 611 reside individually on a plurality of front boards 601, 613, 614, 615, 602. Any number of such satellite management controllers and front boards may be used in some embodiments. The plurality of satellite management controllers 607, 608, 609, 610, 611 are communicatively linked to the routing elements 605, 606 by a plurality of branch segments 625 a-e, 626 a-e. In some embodiments, the plurality of branch segments 625 a-e constitute a single first logical bus, and the corresponding plurality of branch segments 626 a-e constitute a single second logical bus. In such embodiments, all of the communications sent to any management controllers via the first or second logical buses are sent to all management controllers communicatively linked to that logical bus.

In some embodiments, there is a first plurality of logical buses among the first plurality of branch segments 625 a-e, and a second plurality of logical buses among the second plurality of branch segments 626 a-e. A first branch segment 626 a may have its own logical bus; communication sent along the logical branch bus in such an embodiment may be limited to communication to and from the first satellite MC 607 which resides upon a first front board 601. Similarly, a second branch segment 626 b may have its own logical bus, and communications sent along this logical branch bus in such an embodiment may be limited to communication to and from the second satellite MC 608 which resides upon a second front board 613. In some embodiments, each of the branch segments of the first plurality of branch segments 625 a-e is part of a unique logical bus. In some embodiments, each of the branch segments of the second plurality of branch segments 626 a-e is part of a unique logical bus. In some embodiments, there is a plurality of logical buses, but a single logical bus may utilize more than one of the branch segments. In embodiments using a plurality of logical branch buses, the routing element may selectively route communications between the platform control element and the SMCs that are communicatively linked to a particular logical branch bus. The routing element may also selectively route communications from the SMCs that are communicatively linked to a first logical branch bus to the SMCs that are communicatively linked to a second logical branch bus.

In some embodiments, as seen in FIG. 11, a platform management system 1000 utilizes two platform control elements 803, 804 and four routing elements 809, 810, 811, 812. The routing elements 809, 810, 811, 812 reside upon FRUs 805, 806, 807, 808 in this embodiment. In this illustrative embodiment the four routing elements 809, 810, 811, 812 are not located on either of the FRUs 801, 802 upon which the platform control elements 803, 804 are located. In some embodiments, the two platform control elements 803, 804 reside on two separate front boards 801, 802. In some embodiments, the platform control elements reside upon the same FRU. In some embodiments, two or more of the routing elements reside upon the same FRU. In some embodiments, the platform control elements may reside upon a FRU of another type. A first platform control element 804 is communicatively linked to each of two routing elements 809, 810 via duplex root segments 830, 831. A second platform control element 803 is communicatively linked to each of two routing elements 811, 812 via duplex root segments 832, 833. In some embodiments, both of the two platform control elements 803, 804 are adapted to provide central management controller functions on a redundant basis. In some such embodiments, one of the platform control elements is in an active mode while the other platform control element is in a standby mode.

A plurality of satellite management controllers 817, 818, 819, 820 reside individually on a plurality of FRUs 813, 814, 815, 816. In this illustrative example, some of the FRUs 814, 815, 816 are front boards. Any number of such satellite management controllers and front boards may be used in some embodiments. The plurality of satellite management controllers 817, 818, 819, 820 is communicatively linked to the routing elements 809, 810, 811, 812 by a plurality of branch segments. In some embodiments, the plurality of branch segments that are communicatively linked to the A ports of the satellite MCs is part of a first logical bus and the plurality of branch segments that are communicatively linked to the B ports of the satellite MCs is part of a second logical bus. In such embodiments, all of the communications sent to and from the routing elements and all of the satellite management controllers on a particular logical bus are sent to all of the routing elements and all of the satellite management controllers on that same logical bus.

In some embodiments, there are two architectural buses, which may be referred to as the A bus and the B bus. Typically, one of the root segments and corresponding routing element linked to each of the platform control elements will be part of the A architectural bus, while the other root segment and corresponding routing element for each of the platform control elements will be part of the B architectural bus. In such a case, the A routing elements, for example 809, 811, will be communicatively linked to the A ports 817 a, 818 a, 819 a, 820 a of the satellite management controllers, and the B routing elements, for example 810, 812 will be communicatively linked to the B ports 817 b, 818 b, 819 b, 820 b of the satellite management controllers.

In some embodiments, there is a plurality of logical buses among the branch segments. Each physical branch segment may have its own logical bus; communication sent along the branch segment in such an embodiment may be limited to communication to and from a single satellite MC. In some embodiments, there is a plurality of logical buses, but a single logical bus may utilize more than one of the branch segments. In embodiments using a plurality of logical branch buses, the routing element may selectively route communications between the platform control element and the SMCs that are communicatively linked to a particular logical branch bus. The routing element may also selectively route communications from the SMCs that are communicatively linked to a first logical branch bus to the SMCs that are communicatively linked to a second logical branch bus.

In some embodiments, the satellite MCs 817, 818, 819, 820 will have an A port and a B port (4 connector pins total in some such embodiments). In the case of four routing elements, the number of branch segments (4 segments, 8 wires in some such embodiments) coming into the satellite MC may exceed the number of available ports (2 ports, 4 wires in some such embodiments). In such cases, there may be sharing of satellite MC ports between the routing elements. Typically, one of the routing elements linked to each of the platform control elements will be part of the A architectural bus, while the other routing element for each of the platform control elements will be part of the B architectural bus. In such a case, the A routing elements, for example 809, 811, will be communicatively linked to the A ports 817 a, 818 a, 819 a, 820 a of the satellite management controllers, and the B routing elements, for example 810, 812 will be communicatively linked to the B ports 817 b, 818 b, 819 b, 820 b of the satellite management controllers. In some embodiments, the A architectural bus from the first platform control element will be joined with the A architectural bus from the second platform control element at the satellite MC A port, typically by the sharing of a connector pin by two wires (one wire from each of the routing elements associated with that port), with similar connections for the B architectural bus.

In some embodiments, as seen in FIG. 12, a platform management system 1100 utilizes one platform control element and two routing elements. A first platform control element 1102 resides upon a first FRU 1101. In this illustrative embodiment, the platform control element 1102 resides upon a front board. In this embodiment, the first platform control element is adapted to provide central management controller functions.

A first routing element 1105 is communicatively linked to the first platform control element 1102 via a first root segment 1103. The second routing element 1106 is communicatively linked to the first platform control element 1102 via a second root segment 1104. The first routing element 1105 resides upon a second FRU 1107. The second routing element 1106 resides upon a third FRU 1108.

The first routing element 11 05 is communicatively linked to a plurality of satellite management controllers 1111, 1112 via a first plurality of branch segments 1109 a-b. The second routing element 1106 is communicatively linked to a plurality of satellite management controllers 1113, 1114 via a second plurality of branch segments 1110 a-b. The satellite management controllers reside upon on a plurality of FRUs. In this illustrative embodiment, the FRUs 1115, 1116, 1117, 1118 are front boards. The number and type of FRUs may vary across platform management applications, and the number of satellite management controllers may vary across platform management applications. In some embodiments, the platform control element may be linked to more than one routing element. The different routing elements may each be connected to different sets of satellite management controllers.

As evident from the above description, a wide variety of embodiments may be configured from the description given herein and additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is, therefore, not limited to the specific details and illustrative examples shown and described. Accordingly, departures from such details may be made without departing from the spirit or scope of the applicant's general invention. 

1. A platform management system comprising: a first field replaceable unit, said first field replaceable unit comprising: a first platform control element; a second field replaceable unit, said second field replaceable unit comprising: a first routing element, a third field replaceable unit, said third field replaceable unit comprising: a second platform control element; a fourth field replaceable unit, said fourth field replaceable unit comprising: a second routing element; a first root segment, said first root segment adapted to provide a communication link between said first platform control element and said first routing element; and a second root segment, said second root segment adapted to provide a communication link between said second platform control element and said second routing element.
 2. The platform management system of claim 1 further comprising: a plurality of satellite management controllers; a first plurality of branch segments, said first plurality of branch segments adapted to provide communication links between said first routing element and each of said plurality of satellite management controllers; and a second plurality of branch segments, said second plurality of branch segments adapted to provide communication links between said second routing element and each of said plurality of satellite management controllers, wherein said first platform control element and said second control element are adapted to provide central management controller functions for said platform management system.
 3. The platform management system of claim 2 further comprising a plurality of intelligent field replaceable units, wherein one or more of said plurality of satellite management controllers resides upon each of said plurality of intelligent field replaceable units.
 4. The platform management system of claim 3 wherein one or more of said plurality of intelligent field replaceable units is a front board, wherein the front boards are mounted in a subrack.
 5. The platform management system of claim 1 wherein said first platform control element and said second control element are adapted to provide central management controller functions for a plurality of field replaceable units within an electronic platform, and wherein said first platform control element and said second control element are adapted to provide central management controller functions on a redundant basis.
 6. The platform management system of claim 2 wherein said first platform control element and said second control element are adapted to provide central management controller functions on a redundant basis.
 7. The platform management system of claim 2 wherein said first routing element is adapted to selectively route communications between said first platform control element and one or more of said plurality of satellite management controllers.
 8. The platform management system of claim 2 wherein said first routing element is adapted to selectively route communications among the plurality of satellite management controllers.
 9. The platform management system of claim 2 wherein said first plurality of branch segments is segregated into a first plurality of logical branch buses, and wherein said second plurality of branch segments is segregated into a second plurality of logical branch buses.
 10. The platform management system of claim 9 wherein said first routing element is adapted to selectively route communications between said first platform control element and the satellite management controller or controllers that are communicatively linked to one of said first plurality of logical branch buses.
 11. The platform management system of claim 9 wherein said first routing element is adapted to selectively route communications between the satellite management controller or controllers that are communicatively linked to a first logical branch bus of said first plurality of logical branch buses and the satellite management controller or controllers that are communicatively linked to a second logical branch bus of said first plurality of logical branch buses.
 12. The platform management system of claim 2 wherein said second routing element is adapted to selectively route communications between said second platform control element and one or more of said plurality of satellite management controllers.
 13. The platform management system of claim 2 wherein said second routing element is adapted to selectively route communications among the plurality of satellite management controllers.
 14. The platform management system of claim 9 wherein said second routing element is adapted to selectively route communications between said second platform control element and the satellite management controller or controllers that are communicatively linked to one of said second plurality of logical branch buses.
 15. The platform management system of claim 9 wherein said second routing element is adapted to selectively route communications between the satellite management controller or controllers that are communicatively linked to a first logical branch bus of said second plurality of logical branch buses and the satellite management controller or controllers that are communicatively linked to a second logical branch bus of said second plurality of logical branch buses.
 16. The platform management system of claim 4 wherein one or more of said first, second, third and fourth field replaceable units are mounted outside the subrack that holds the front boards.
 17. A platform management system comprising: a first field replaceable unit, said first field replaceable unit comprising a first platform control element; a second field replaceable unit, said second field replaceable unit comprising a first routing element, wherein no platform control element resides upon said second field replaceable unit; and a first root segment, said first root segment adapted to provide a communication link between said first platform control element and said first routing element.
 18. The platform management system of claim 17 further comprising: a plurality of satellite management controllers; and a plurality of branch segments, said plurality of branch segments adapted to provide communication links between said first routing element and each of said plurality of satellite management controllers, wherein said first platform control element is adapted to provide central management controller functions for said platform management system.
 19. The platform management system of claim 18 further comprising a plurality of intelligent field replaceable units, wherein one or more of said plurality of satellite management controllers resides on each of said plurality of intelligent field replaceable units.
 20. The platform management system of claim 19 wherein one or more of said plurality of intelligent field replaceable units is a front board, wherein the front boards are mounted in a subrack.
 21. The platform management system of claim 18 wherein said first routing element is adapted to selectively route communications between said first platform control element and one or more of said plurality of satellite management controllers.
 22. The platform management system of claim 18 wherein said first routing element is adapted to selectively route communications among the plurality of satellite management controllers.
 23. The platform management system of claim 18 wherein said first plurality of branch segments is segregated into a first plurality of logical branch buses.
 24. The platform management system of claim 23 wherein said first routing element is adapted to selectively route communications between said first platform control element and the satellite management controller or controllers that are communicatively linked to one of said first plurality of logical branch buses.
 25. The platform management system of claim 23 wherein said first routing element is adapted to selectively route communications between the satellite management controller or controllers that are communicatively linked to a first logical branch bus of said first plurality of logical branch buses and the satellite management controller or controllers that are communicatively linked to a second logical branch bus of said first plurality of logical branch buses.
 26. The platform management system of claim 20 wherein one or more of said first and second field replaceable units are mounted outside the subrack that holds the front boards.
 27. A platform management system comprising: a first field replaceable unit, said first field replaceable unit comprising a first platform control element; and a second field replaceable unit, said second field replaceable unit comprising a first routing element; a third field replaceable unit, said third field replaceable unit comprising a second routing element; a first root segment, said first root segment adapted to provide a communication link between said first platform control element and said first routing element; and a second root segment, said second root segment adapted to provide a communication link between said first platform control element and said second routing element.
 28. The platform management system of claim 27 further comprising: a plurality of satellite management controllers, a first plurality of branch segments, said first plurality of branch segments adapted to provide communication links between said first routing element and each of said plurality of satellite management controllers; and a second plurality of branch segments, said second plurality of branch segments adapted to provide communication links between said second routing element and each of said plurality of satellite management controllers, wherein said first platform control element is adapted to provide central management controller functions for said platform management system.
 29. The platform management system of claim 28 wherein each satellite management controller comprises two ports, and wherein each satellite management controller is communicatively linked to one of the first plurality of branch segments via a first port and to one of the second plurality of branch segments via a second port.
 30. The platform management system of claim 28 further comprising a plurality of intelligent field replaceable units, wherein one or more of said plurality of satellite management controllers resides on each of said plurality of intelligent field replaceable units.
 31. The platform management system of claim 30 wherein one or more of said plurality of intelligent field replaceable units is a front board, wherein the front boards are mounted in a subrack.
 32. The platform management system of claim 28 wherein said first routing element is adapted to selectively route communications between said first platform control element and one or more of said plurality of satellite management controllers.
 33. The platform management system of claim 28 wherein said first routing element is adapted to selectively route communications among the plurality of satellite management controllers.
 34. The platform management system of claim 28 wherein said second routing element is adapted to selectively route communications between said first platform control element and one or more of said plurality of satellite management controllers.
 35. The platform management system of claim 28 wherein said second routing element is adapted to selectively route communications among the plurality of satellite management controllers.
 36. The platform management system of claim 28 wherein said first plurality of branch segments are segregated into a first plurality of logical branch buses.
 37. The platform management system of claim 28 wherein said second plurality of branch segments are segregated into a second plurality of logical branch buses.
 38. The platform management system of claim 36 wherein said first routing element is adapted to selectively route communications between said first platform control element and the satellite management controller or controllers that are communicatively linked to one of said first plurality of logical branch buses.
 39. The platform management system of claim 36 wherein said first routing element is adapted to selectively route communications between the satellite management controller or controllers that are communicatively linked to a first logical branch bus of said first plurality of logical branch buses and the satellite management controller or controllers that are communicatively linked to a second logical branch bus of said first plurality of logical branch buses.
 40. The platform management system of claim 37 wherein said second routing element is adapted to selectively route communications between said first platform control element and the satellite management controller or controllers that are communicatively linked to one or more of said second plurality of logical branch buses.
 41. The platform management system of claim 37 wherein said second routing element is adapted to selectively route communications between the satellite management controller or controllers that are communicatively linked to a first logical branch bus of said second plurality of logical branch buses and the satellite management controller or controllers that are communicatively linked to a second logical branch bus of said second plurality of logical branch buses.
 42. The platform management system of claim 31 wherein one or more of said first, second and third field replaceable unit are mounted outside the subrack that holds the front boards.
 43. The platform management system of claim 27 further comprising: a fourth field replaceable unit, said fourth field replaceable unit comprising a second platform control element a third root segment, said third root segment adapted to provide a communication link between said second platform control element and said first routing element; and a fourth root segment, said fourth root segment adapted to provide a communication link between said second platform control element and said second routing element.
 44. The platform management system of claim 28 further comprising: a fourth field replaceable unit, said fourth field replaceable unit comprising a second platform control element a third root segment, said third root segment adapted to provide a communication link between said second platform control element and said first routing element; and a fourth root segment, said fourth root segment adapted to provide a communication link between said second platform control element and said second routing element, wherein said first platform control element and said second platform control element are adapted to provide central management controller functions for said platform management system.
 45. The platform management system of claim 44, wherein said first platform control element and said second platform control element are adapted to provide central management controller functions on a redundant basis.
 46. A platform management system comprising: a first field replaceable unit, said first field replaceable unit comprising a first platform control element; a second field replaceable unit, said second field replaceable unit comprising a second platform control element a third field replaceable unit, said third field replaceable unit comprising a first routing element; a fourth field replaceable unit, said fourth field replaceable unit comprising a second routing element; a fifth field replaceable unit, said fifth field replaceable unit comprising a third routing element; a sixth field replaceable unit, said sixth field replaceable unit comprising a fourth routing element; a first root segment, said first root segment adapted to provide a communication link between said first platform control element and said first routing element; a second root segment, said second root segment adapted to provide a communication link between said first platform control element and said second routing element; a third root segment, said third root segment adapted to provide a communication link between said second platform control element and said third routing element; and a fourth root segment, said fourth root segment adapted to provide a communication link between said second platform control element and said fourth routing element.
 47. The platform management system of claim 46 further comprising: a plurality of satellite management controllers; a first plurality of branch segments, said first plurality of branch segments adapted to provide communication links between said first routing element and each of said plurality of satellite management controllers; a second plurality of branch segments, said second plurality of branch segment adapted to provide communication links between said second routing element and each of said plurality of satellite management controllers; a third plurality of branch segments, said third plurality of branch segments adapted to provide communication links between said third routing element and each of said plurality of satellite management controllers; and a fourth plurality of branch segments, said fourth plurality of branch segments adapted to provide communication links between said fourth routing element and each of said plurality of satellite management controllers, wherein said first platform control element and said second platform control element are adapted to provide central management controller functions for said platform management system.
 48. The platform management system of claim 47 wherein said first platform control element and said second control element are adapted to provide central management controller functions on a redundant basis.
 49. The platform management system of claim 47 wherein said first routing element is adapted to selectively route communications between said first platform control element and one or more of said plurality of satellite management controllers.
 50. The platform management system of claim 47 wherein said second routing element is adapted to selectively route communications between said first platform control element and one or more of said plurality of satellite management controllers.
 51. The platform management system of claim 47 wherein said third routing element is adapted to selectively route communications between said second platform control element and one or more of said plurality of satellite management controllers.
 52. The platform management system of claim 47 wherein said fourth routing element is adapted to selectively route communications between said second platform control element and one or more of said plurality of satellite management controllers.
 53. The platform management system of claim 47 wherein each satellite management controller comprises two ports, wherein said first plurality of branch segments and said third plurality of branch segments link to a first port of said plurality of satellite management controllers.
 54. The platform management system of claim 53 wherein each satellite management controller comprises two branch bus ports, and wherein said second plurality of branch segments and said fourth plurality of branch segments link to a second port of said plurality of satellite management controllers.
 55. The platform management system of claim 47 further comprising a plurality of intelligent field replaceable units, wherein one or more of said plurality of satellite management controllers resides on each of said plurality of intelligent field replaceable units.
 56. The platform management system of claim 55 wherein one or more of said plurality of intelligent field replaceable units is a front board, wherein the front boards are mounted in the subrack.
 57. The platform management system of claim 56 wherein one or more of said first, second, third, fourth, fifth and sixth field replaceable units are mounted outside the subrack that holds the front boards.
 58. The platform management system of claim 47 wherein said first platform control element and said second platform control element are adapted to provide central management controller functions on a redundant basis.
 59. The platform management system of claim 58 wherein said first plurality of branch segments and said third plurality of branch segments are segregated into a first plurality of logical branch buses.
 60. The platform management system of claim 59 wherein said second plurality of branch segments and said fourth plurality of branch segments are segregated into a second plurality of logical branch buses
 61. The platform management system of claim 59 wherein said first routing element is adapted to selectively route communications between said first platform control element and the satellite management controller or controllers linked to one or more of said first plurality of logical branch buses.
 62. The platform management system of claim 60 wherein said second routing element is adapted to selectively route communications between said first platform control element and the satellite management controller or controllers linked to one or more of said second plurality of logical branch buses.
 63. The platform management system of claim 59 wherein said third routing element is adapted to selectively route communications between said second platform control element and the satellite management controller or controllers linked to one or more of said first plurality of logical branch buses.
 64. The platform management system of claim 60 wherein said fourth routing element is adapted to selectively route communications between said second platform control element and the satellite management controller or controllers linked to one or more of said second plurality of logical branch buses.
 65. The platform management system of claim 59 wherein said first routing element is adapted to selectively route communications among the satellite management controller or controllers that are communicatively linked to a first logical branch bus of said first plurality of logical branch buses and the satellite management controller or controllers that are communicatively linked to a second logical branch bus of said first plurality of logical branch buses.
 66. The platform management system of claim 60 wherein said second routing element is adapted to selectively route communications among the satellite management controller or controllers that are communicatively linked to a first logical branch bus of said second plurality of logical branch buses and the satellite management controller or controllers that are communicatively linked to a second logical branch bus of said second plurality of logical branch buses.
 67. The platform management system of claim 59 wherein said third routing element is adapted to selectively route communications among the satellite management controller or controllers that are communicatively linked to a first logical branch bus of said first plurality of logical branch buses and the satellite management controller or controllers that are communicatively linked to a second logical branch bus of said first plurality of logical branch buses.
 68. The platform management system of claim 60 wherein said fourth routing element is adapted to selectively route communications among the satellite management controller or controllers that are communicatively linked to a first logical branch bus of said second plurality of logical branch buses and the satellite management controller or controllers that are communicatively linked to a second logical branch bus of said second plurality of logical branch buses.
 69. The platform management system of claim 47 wherein one or more of said first, second, third and fourth routing elements are adapted to selectively route communications among the plurality of satellite management controllers.
 70. A platform management system comprising: a first field replaceable unit, said first field replaceable unit comprising a first platform control element; and a second field replaceable unit, said second field replaceable unit comprising a first routing element; a third field replaceable unit, said third field replaceable unit comprising a second routing element; a first root segment, said first root segment adapted to provide a communication link between said first platform control element and said first routing element; a second root segment, said second root segment adapted to provide a communication link between said first platform control element and said second routing element; a first plurality of satellite management controllers; a second plurality of satellite management controllers; a first plurality of branch segments, said first plurality of branch segments adapted to provide communication links between said first routing element and each of said first plurality of satellite management controllers; and a second plurality of branch segments, said second plurality of branch segments adapted to provide communication links between said second routing element and each of said second plurality of satellite management controllers, wherein said first platform control element is adapted to provide central management controller functions for said platform management system. 